Many eye diseases can be treated with laser radiation. A prominent example is cataract surgery, i.e., the exchange of the impaired eye lens for an implant. Treatment laser radiation is focused into the eye of the patient in order to produce cuts at predefined locations and to enable the impaired eye lens to be removed. The treatment laser radiation is focused into the eye and the focus position is shifted in the eye. For this, a laser scanner is provided, which scans the laser radiation over the eye, for example, to apply a pulsed laser radiation in the lens of the eye by shifting the focus position such that this lens can be comminuted and removed.
For the action of the laser radiation, in particular pulsed laser radiation, the target points for the focus position must be directed precisely to specified structures of the eye. It is therefore known to produce a three-dimensional image at least of the specified structures of the eye, in some cases even of the whole eye, by means of optical coherence tomography. A respective method and device are known from US 2013/0102895 A1. There the beam path of an OCT module is combined with the beam path of the treatment laser radiation and then supplied to the laser scanner. It is thereby achieved that the OCT imaging takes place at exactly the same location as that to which the treatment laser radiation is also focused. A systematically similar construction is known from U.S. Pat. No. 8,409,921 B1, which likewise combines the beam path of an OCT with the beam path of a treatment laser and deflects it in the eye via a common laser scanner.
In both of the named devices, a contact lens can be used in order to make a coupling-in of the radiation into the eye easier and in particular to fix the eye spatially. According to US 2013/0102895 A1, adjustment marks can be provided on the contact lens which are made to coincide with markings applied to the cornea before surgery, in order to bring the eye into the correct position with respect to the laser treatment system. The correct position of the eye can be checked with an additional camera, which generates a wide image of the contact lens and the cornea. For the adjustment process, U.S. Pat. No. 8,409,921 B1 uses a separate surgical microscope, which is used before the laser treatment system and, after suitable examination of the eye, is replaced by the laser treatment system.
US 2009/0137993 A1 likewise relates to a laser treatment system which uses treatment laser radiation to modify certain structures of the eye. Here, the treatment progress can be observed by means of an optical coherence tomograph (OCT) or a camera, and in particular the focal position of the treatment laser beam can be checked during the treatment. The OCT or the camera also images the area of the eye in which the focus is shifted. The OCT and the laser treatment device can be present as separate or as combined systems. If both systems use the same contact lens, the OCT can be used in order not only to capture selected areas of specified eye structures which are to be treated, but also to image selected areas of the contact lens. In all embodiments of US 2009/0137993, in particular in the embodiments in which separate scanners are used in each case for treatment laser radiation and OCT imaging, the OCT serves to check the position of the focus of the treatment laser radiation in the specified structures of the eye in that the OCT images precisely these specified structures during the treatment procedure.
In order to rule out misalignments of the focus of the treatment laser radiation in the eye, in the state of the art according to US 2009/0137993 A1 it is necessary to image the corresponding eye structures using optical coherence tomography simultaneously as far as possible. In time periods in which no OCT imaging takes place, the position of the focus of the treatment laser radiation with respect to the specified structures to be treated cannot be monitored. Any movements of the eye during such time periods would lead to a misalignment of the focus of the treatment laser radiation.